The invention relates to a method and a device for optical in vitro detection of a movement in a biological sample with a spatial extent.
It is known from practice that a requirement for monitoring the active dynamics of closed and three-dimensional cell and tissue cultures in areas such as development biology, toxicity testing and pharmaceutical research exists.
Tissue samples bred from embryonic stem cells that have differentiated into muscle tissue are for example used as part of toxicity tests in order to check the harmfulness of a substance to be tested. It is investigated here whether a substance applied to the muscle tissue influences the muscle contraction of the muscle tissue, which can be an indicator for the toxicity of the substance. Measuring methods are required for this in order to detect a movement, for example a contraction, in such a three-dimensional biological sample in the form of a cell cluster. Typical diameters of such cell clusters are 100 to 400 μm, whilst diameters within the millimeter range are also possible.
These studies are currently carried out mainly using visual observation and more rarely by using video microscopy with subsequent image analysis. The first is time consuming and is always connected with subjective assessment. The latter has the disadvantage that complex imaging optics and a complex image analysis connected with substantial research effort are required. Their inherent sensitivity towards small displacements is a further disadvantage.
Non-optical methods such as impedance measurements work only in contact with the sample. If the sample form does however deviate from the level (adherent monolayer) or is even three-dimensional, and also swims freely in a medium, the above mentioned techniques cannot be applied.
Automated imaging methods have the disadvantage that 10 to 40 image levels of the sample must for example be measured for a focal depth of 10 μm and the above mentioned typical size of the cell cluster of 100 to 400 μm. Given a typical minimum measuring period of approx. 10 seconds for being able to detect a movement and the additional time required for re-positioning or focusing, such methods are not suitable for quickly monitoring a multitude of samples.
A serial measurement of large numbers of samples is generally not indicated in view of the rather long monitoring period due to the time scales of biological dynamics. In practice, there is however a need to carry out such movement detection for a multitude of samples that are separate from each other, for example stored in a multi-well plate, also known as a micro-titer plate, for example with 96 or 384 cavities (English: wells). Imaging methods are not suitable for a parallel measurement of a multitude of such samples, as it is difficult to realize an arrangement of an imaging optical device at every cavity of the multi-well plate for geometric reasons and a lack of construction space.
It is therefore an objective of the invention to provide an improved method for detecting a movement in a biological sample with a spatial extent, with which the disadvantages of conventional techniques can be avoided. The invention is in particular based on the objective of providing a robust, contactless method for movement detection that requires no complex image analysis. It is a further objective of the invention to provide a method that is suitable for the parallel analysis of a multitude of samples in a screening environment. A further objective consists of providing a device for the detection of a movement in a biological sample with a spatial extent, with which disadvantages of conventional devices can be avoided.
These objectives are solved by devices and methods of the invention. Advantageous embodiments and applications of the invention. Advantageous embodiments and applications of the invention will be explained in more detail in the following description with partial reference to the Figures.